Radical Reactions with N-Heterocyclic Carbene (NHC)-Derived Acyl Azoliums for Access to Multifunctionalized Ketones

As one of the most important key intermediates, NHC-bound acylazolium-based ionic transformations have been intensively explored in the past two decades. With the expeditious development of NHC-catalyzed radical transformations in recent years, NHC-bound acylazolium chemistry has reached another level, with the number of relevant publications increasing significantly. However, a summary focused on radical acylations of NHC-derived acyl azoliums classified according to the mechanistic difference has not been reported. Such a detailed classification and deep analysis provide opportunities for a better understanding of the history and trend of this field. In this review, radical reactions with N-heterocyclic carbene (NHC)-derived acyl azoliums are systematically introduced. The achievements and challenges within this area are also summarized and discussed at the end.